1. Field of the Invention
The present invention relates to a road white line detecting apparatus and method using a CCD (Charge Coupled Device) camera and, more particularly, relates to road white line detecting apparatus and method which are capable of accurately detecting a position of the white line without an erroneous detection of edges of a smear developed on the CCD camera as the road white line.
2. Description of the Related Art
Recently, in order to achieve an automatic drive of an automotive vehicle or in order to assist a vehicular driver's driving of the vehicle, a video image outputted from a camera mounted on a vehicle is processed to detect such a white line as described above or to extract an image of a preceding vehicle running ahead of the vehicle (so-called, a host vehicle) from the image outputted from the camera. However, although it is ideal that a luminance state is stable during such an image processing as described above, such a stable luminance cannot always be achieved depending upon a usage environment.
For example, while the road white line is detected using the CCD camera mounted on a vehicle body, a strong light source is present within a photograph range due to a presence of a light source itself, such as the sun and a headlight from an opposing vehicle which is running toward the vehicle at an opposing lane adjacent to the traffic lane of the host vehicle and due to reflections of light beams on a surrounding construction (building) and some of other vehicles. Consequently, such a smear phenomenon that white rays of light are extended from the strong light source occurs in a charge transfer direction of the CCD camera.
There is a high possibility that an erroneous detection of the white line occurs since the smear on the photographed image has the similar feature as the white line while a detection of white line is carried out. This provides a problem in a vehicular system having a traffic lane missing alarm system or lane keep assistance function. Hence, an automotive industry has demanded that the road white line should accurately be detected without a mistake that the smear edge is the white line.
A Japanese Patent Application First Publication No. Heisei 9-190537 published on Jun. 2, 1998 exemplifies a previously proposed on-vehicle road white line detecting apparatus.
In the previously proposed road white line detecting apparatus disclosed in the above-described Japanese Patent Application First Publication, such a fact that the smear is developed due to a saturation of a charge in the CCD camera and a pixel value thereof is nearer to a saturation level than that of the white line is utilized. Then, the previously proposed road white line detecting apparatus determines the presence of the white line only when the pixel value of the line edge is strong and the pixel value on the white line is smaller than a predetermined threshold value.